Chromosomal localization of several human onc gene analogues has been carried out using human-rodent somatic cell hybrids. The following have been mapped: N-ras, chromosome 1; Ki-ras 1, chromosome 6; Ki-ras 2 and 3, chromosome 12; myc, chromosome 8; abl, chromosome 9; bas, chromosome 11. Two rearranged myc loci from Raji Burkitt's lymphoma have been cloned and characterized.